1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583
2. Center for Sensors and MEMS, National University of Singapore, 4 Engineering Drive 3, Singapore 117583
3. National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan